1. Field
Methods and apparatuses consistent with one or more exemplary embodiments relate to a laser speckle interferometric system and method, and more particularly, to a laser speckle interferometric system for monitoring a parameter of a biological object by using a mobile device and a laser speckle interferometric method.
2. Description of the Related Art
In laser speckle interferometry, secondary interferometric (i.e., “speckle”) patterns are detected and processed. A speckle pattern is formed by scattering of coherent radiation from a rough surface. Laser speckle interferometry has been widely used to monitor engineering parameters and various parameters of biological objects, and the parameters of the biological objects includes variables such as blood pressure, pulse rate, blood flow velocity, and skin condition of a person. Laser speckle interferometry can be performed with non-contact and non-invasive application, high sensitivity, and may be simply implemented.
However, as an existing laser speckle interferometric system is affected by vibration, research into biological parameters using such system has been limited. The vibration problem may be solved by firmly fixing an object under laboratory conditions. In some cases, unfortunately, this solution may be impractical, for example, when parameters of a human body are monitored. Recently, laser speckle interferometry has been used to extract information about pulses and pulse pressure (refer to Yevgeny Beiderman, Israel Horovitz et al., Remote Estimation of Blood Pulse Pressure via Temporal Tracking of Reflected Secondary Speckles Pattern/Journal of Biomedical Optics, 2010, 15(6) 061707), but successful implementation of the laser speckle interferometry uses a tight fixation of a human's arm while extracting the information.
Reference 1 (US 20130144137, METHOD AND SYSTEM FOR NON-INVASIVELY MONITORING BIOLOGICAL OR BIOCHEMICAL PARAMETERS OF INDIVIDUAL, Bar Ilan University, Universitat De Valencia (2012)) discloses a method and system for tracking one or more parameters of a human body. The system includes a controller including an input port for receiving image data, a memory unit, and a processor. Graphic data indicates information collected by a detector in which pixels are arranged and is in the form of a sequence of a speckle pattern formed by scattering, in a portion of the human body, coherent radiation irradiated at predetermined intervals towards the portion. The memory unit stores one or more predetermined models, and the predetermined models include measurable parameters and data representing a relationship between one or more parameters of the human body. The processor is configured to process image data, calculate a spatial correlation function between neighboring speckle patterns through time-series calculation of the spatial correlation function in the form of a time-varying function of at least one parameter of a correlation function, select at least one parameter of a time-varying spatial correlation function in order to determine one or more corresponding parameters of the human body and generate output data corresponding to parameters of the human body to be examined, and apply the at least one selected parameter to one or more preliminary models. The time-varying spatial correlation function represents a temporal change in the speckle pattern. It may be difficult to apply the system and method of reference 1 to a mobile device due to the lack of a vibration reduction device.
Reference 2 (US 20110013002, LASER SPECKLE IMAGING SYSTEMS AND METHODS, Ind Res Ltd, Oliver Bendix Thompson, Michael Kenneth Andrews (2009)) discloses a system and method of measuring perfusion of biological tissues. The disclosed method includes recording images of tissues on which a laser beam is irradiated, providing contrast images of the tissues, determining a power spectrum of radiation scattered from the contrast images, and determining perfusion of the power spectrum. The system includes a processor configured to control a digital video camera, a laser light source, and a camera, produce images with different exposure times, obtain images from the camera, process image data to determine the power spectrum of the radiation, and determine perfusion values of the power spectrum. The above-described method is designed to measure blood flow in tissues of a human body, but may not be sufficient to accurately measure the blood pressure. Also, it may be difficult to apply the method to a mobile device due to the lack of a vibration reduction device.
Reference 3 (U.S. Pat. No. 7,925,056, OPTICAL SPECKLE PATTERN INVESTIGATION, Koninklijke Philips Electronics N.V (2011)) discloses a system and method for medical equipment used for non-invasive in vivo measurement of at least one parameter or a state of a subject having a scattering medium in a target region. The system includes an illumination system, a detection system, and a control system. The illumination system includes at least one light source for generating partially or entirely coherent light to illuminate a region of a human body to cause a light response from the illuminated region. The detection system includes at least one radiation detector for recording a time-varying intensity variation of the light response, and generates data regarding a measurement result of dynamic light scattering. The control system is configured to receive and analyze the measurement result of the dynamic light scattering to determine at least one parameter and generate output data. However, it may be difficult to apply this method to a mobile device due to the lack of a vibration reduction device.